Category: Papers

The Inherent Instability of Disordered Systems

The Multiscale Law of Requisite Variety is a scientific law relating, at each scale, the variation in an environment to the variation in internal state that is necessary for effective response by a system. While this law has been used to describe the effectiveness of systems in self-regulation, the consequences for failure have not been formalized. Here we use this law to consider the internal dynamics of an unstructured system, and its response to a structured environment. We find that, due to its inability to respond, a completely unstructured system is inherently unstable to the formation of structure. And in general, any system without structure above a certain scale is unable to withstand structure arising above that scale. To describe complicated internal dynamics, we develop a characterization of multiscale changes in a system. This characterization is motivated by Shannon information theoretic ideas of noise, but considers structured information. We then relate our findings to political anarchism showing that society requires some organizing processes, even if there is no traditional government or hierarchies. We also formulate our findings as an inverse second law of thermodynamics; while closed systems collapse into disorder, systems open to a structured environment spontaneously generate order.


Taeer Bar-Yam, Owen Lynch, Yaneer Bar-Yam, The inherent instability of disordered systems, arXiv:1812.00450


Stability of democracies: a complex systems perspective

The idea that democracy is under threat, after being largely dormant for at least 40 years, is looming increasingly large in public discourse. Complex systems theory offers a range of powerful new tools to analyse the stability of social institutions in general, and democracy in particular. What makes a democracy stable? And which processes potentially lead to instability of a democratic system? This paper offers a complex systems perspective on this question, informed by areas of the mathematical, natural, and social sciences. We explain the meaning of the term ‘stability’ in different disciplines and discuss how laws, rules, and regulations, but also norms, conventions, and expectations are decisive for the stability of a social institution such as democracy.


Stability of democracies: a complex systems perspective
K Wiesner, A Birdi3, T Eliassi-Rad, H Farrell, D Garcia, S Lewandowsky, P Palacios, D Ross, D Sornette and K Thébault
European Journal of Physics, Volume 40, Number 1


Consciousness: The last 50 years (and the next)

The mind and brain sciences began with consciousness as a central concern. But for much of the 20th century, ideological and methodological concerns relegated its empirical study to the margins. Since the 1990s, studying consciousness has regained a legitimacy and momentum befitting its status as the primary feature of our mental lives. Nowadays, consciousness science encompasses a rich interdisciplinary mixture drawing together philosophical, theoretical, computational, experimental, and clinical perspectives, with neuroscience its central discipline. Researchers have learned a great deal about the neural mechanisms underlying global states of consciousness, distinctions between conscious and unconscious perception, and self-consciousness. Further progress will depend on specifying closer explanatory mappings between (first-person subjective) phenomenological descriptions and (third-person objective) descriptions of (embodied and embedded) neuronal mechanisms. Such progress will help reframe our understanding of our place in nature and accelerate clinical approaches to a wide range of psychiatric and neurological disorders.


Consciousness: The last 50 years (and the next)
Anil K. Seth
Brain and Neuroscience Advances


Beyond Calories: A Holistic Assessment of the Global Food System

The global food system is failing to meet nutritional needs, with growing concerns for health related to both under-, over-consumption and severe micronutrient deficiency. The 2nd Sustainable Development Goal (SDG2) targets the end of malnutrition in all forms by 2030. To address this challenge, the focus around food security and malnutrition must be broadened beyond the scope of sufficient energy intake to take full account of total nutrient supply and requirements. Here, for the first time, we have quantitatively mapped the global food system in terms of energy, protein, fat, essential amino acids, and micronutrients from “field-to-fork,” normalized to an equitable per capita availability metric. This framework allows for the evaluation of the sufficiency of nutrient supply, identifies the key hotspots within the global food supply chain which could be targeted for improved efficiency, and highlights the trade-offs which may arise in delivering a balanced nutritional system.


Beyond Calories: A Holistic Assessment of the Global Food System

Hannah Ritchie, David S. Reay and Peter Higgins

Front. Sustain. Food Syst.


A structural transition in physical networks

In many physical networks, including neurons in the brain1,2, three-dimensional integrated circuits3 and underground hyphal networks4, the nodes and links are physical objects that cannot intersect or overlap with each other. To take this into account, non-crossing conditions can be imposed to constrain the geometry of networks, which consequently affects how they form, evolve and function. However, these constraints are not included in the theoretical frameworks that are currently used to characterize real networks5,6,7. Most tools for laying out networks are variants of the force-directed layout algorithm8,9—which assumes dimensionless nodes and links—and are therefore unable to reveal the geometry of densely packed physical networks. Here we develop a modelling framework that accounts for the physical sizes of nodes and links, allowing us to explore how non-crossing conditions affect the geometry of a network. For small link thicknesses, we observe a weakly interacting regime in which link crossings are avoided via local link rearrangements, without altering the overall geometry of the layout compared to the force-directed layout. Once the link thickness exceeds a threshold, a strongly interacting regime emerges in which multiple geometric quantities, such as the total link length and the link curvature, scale with the link thickness. We show that the crossover between the two regimes is driven by the non-crossing condition, which allows us to derive the transition point analytically and show that networks with large numbers of nodes will ultimately exist in the strongly interacting regime. We also find that networks in the weakly interacting regime display a solid-like response to stress, whereas in the strongly interacting regime they behave in a gel-like fashion. Networks in the weakly interacting regime are amenable to 3D printing and so can be used to visualize network geometry, and the strongly interacting regime provides insights into the scaling of the sizes of densely packed mammalian brains.


A structural transition in physical networks
Nima Dehmamy, Soodabeh Milanlouei & Albert-László Barabási 
Nature volume 563, pages 676–680 (2018)